The present invention relates to the field of semiconductor design, semiconductor design testing, and semiconductor manufacture. In particular the present invention discloses methods for estimating various electrical and physical properties of semiconductor integrated circuit designs.
Complex digital integrated circuits (xe2x80x9cICsxe2x80x9d) are initially designed using high-level logic elements such as adders, arithmetic/logic units (ALUs), memory units, buses, etc. These high level elements are in turn constructed from lower level components such as AND gates, OR gates, inverters, etc. These lower level components are constructed from basic electronic components such as transistors, diodes, and electrical conductive traces. All of these electronic and circuit components of ICs are jointly referred to as xe2x80x9ccomponents.xe2x80x9d
Design engineers design an integrated circuit by transforming a circuit description of the integrated circuit into geometric descriptions of physical components that create the basic electronic components. The detailed geometric descriptions of physical components are referred to as integrated circuit layouts.
To create the integrated circuit layout for a complex integrated circuit, circuit design engineers use Electronic Design Automation (xe2x80x9cEDAxe2x80x9d) application programs. These EDA application programs are computer-based tools for creating, editing, and analyzing integrated circuit design layouts.
It is a layout EDA application program that creates a physical integrated circuit design layout from a logical circuit design. The layout EDA application uses geometric shapes of different materials to create the various electrical components on an integrated circuit. For instance, EDA tools commonly use rectangular lines to represent the passive wire segments (conductors) that interconnect the active integrated circuit components such as transistors. These EDA tools also represent electronic and circuit IC components as geometric objects with varying shapes and sizes.
After an initial integrated circuit layout has been created, the integrated circuit layout is tested and optimized using a set of EDA testing tools. Common testing and optimization steps include extraction, verification, and compaction. The steps of extraction and verification are performed to ensure that the integrated circuit layout will perform as desired. The test of extraction is the process of analyzing the geometric layout and material composition of an integrated circuit layout in order to xe2x80x9cextractxe2x80x9d electrical characteristics of the integrated circuit layout. The step of verification uses the extracted electrical characteristics to analyze the circuit design using circuit analysis tools.
Common electrical characteristics that are extracted from an integrated circuit layout include capacitance and resistance of the various xe2x80x9cnetsxe2x80x9d (electrical interconnects) in the integrated circuit. These electrical characteristics are sometimes referred to as xe2x80x9cparasiticxe2x80x9d since these are electrical characteristics are not intended by the designer but result from the underlying physics of the integrated circuit design.
For example, when an electrical circuit designer wishes to connect two different locations of an integrated circuit with an electrical conductor, the electrical circuit designer would ideally like perfect conductor with zero resistance and zero capacitance. However, the geometry of a real conductor, its material composition, and its interaction with other nearby circuit elements will create some parasitic resistance and parasitic capacitance. The parasitic resistance and parasitic capacitance affect the operation of the designed integrated circuit. Thus, the effect of the parasitic resistance and parasitic capacitance affect must be considered.
To test an integrated circuit layout, the parasitic resistance and parasitic capacitance are xe2x80x9cextractedxe2x80x9d from the integrated circuit layout and then the integrated circuit is analyzed and possibly simulated with a using the extracted parasitic resistance and parasitic capacitance. If the parasitic resistance or parasitic capacitance cause undesired operation, then the integrated circuit layout must be changed. Furthermore, minimizing the amount of parasitic resistance and parasitic capacitance can optimize the performance of the integrated circuit.
Extracting the electrical characteristics of the integrated circuit layout (such as capacitance, resistance, and inductance) is an extremely difficult task. Most existing extraction systems approximate sections of an integrated circuit with similar geometric configurations having known electrical characteristics. Interpolation between various different similar geometric configurations is used to further refine extracted electrical characteristics.
The existing extraction techniques have been adequate but are increasingly becoming problematic as the feature size of the electrical components on integrated circuits grow ever smaller. With the very small feature size of current and upcoming semiconductor processes, the accurate extraction of electrical characteristics from integrated circuit layouts becomes critical. Thus, it would be desirable to implement new integrated circuit extraction methods that are both accurate and fast.
The present invention introduces a novel method of performing integrated circuit layout extraction using machine-learning. The system of the present invention has two main phases: model creation and model application.
The model creation phase comprises creating one or more extraction models using machine-learning techniques. First, a complex extraction problem is decomposed into smaller simpler extraction problems. Each smaller extraction problem is then analyzed to identify a set of parameters that fully define the smaller extraction problem. Then, models are created using machine learning techniques for all of the smaller simpler extraction problems.
The machine learning is performed by first creating training data sets composed of the identified parameters from typical examples of the smaller extraction problem and the answers to those example extraction problems as solved using a highly accurate physics based field solver. The training sets are then used to train the models. In one embodiment, neural networks are used to model the extraction problems. To train the neural network models, Bayesian inference is used in one embodiment. Bayesian inference may be implemented with normal Monte Carlo techniques or Hybrid Monte Carlo techniques. After the creation of a set of models for each of the smaller simpler extraction problems, the machine-learning based models may be used for extraction.
To apply the machine-learning based extraction models, the extraction software first decomposes a larger extraction problem from an integrated circuit layout into the various different smaller simpler extraction problems previously identified. Then, for each smaller simpler extraction problem, the extraction software selects the parameters that define that smaller simpler extraction problem from the integrated circuit layout. The extraction software then supplies the parameters to the machine-learning based extraction model trained for such a smaller simpler extraction problem.